CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 7, August 2012
380
AFRICA
early detection and treatment of hypertension before progression
to complications of TOD, which portends a poor prognosis.
There are few studies on target-organ involvement in
hypertensive Nigerian patients at the secondary and tertiary level
of care,
12-14
but few or none in the general population and in the
primary-care setting. The aim of our study was to evaluate the
prevalence of TOD and established CVD in a hypertensive adult
Nigerian population, using methods that could easily be adopted
at the primary health centre (PHCs) level. This would be helpful
to the health planners for formulation and implementation of
preventative strategies.
Methods
This work was part of a community-based, descriptive,
non-interventional, cross-sectional survey of cardiometabolic
risk factors, conducted from December 2002 to November 2005
in the Egbeda local government area (ELGA), a rural community
in south-western Nigeria, with a population of 128 000. The
local governments are serviced by PHCs which are meant to
serve as the initial point of care for the majority of patients in
Nigeria. The study protocol was evaluated and approved by the
Ethics of Human Research Committee of the State Ministry of
Health. Individual consent was obtained verbally and where
possible by written consent.
Four hundred and fifteen confirmed hypertensive adults (184
males and 231 females) above 18 years of age who participated
in the cross-sectional, community-based survey formed the
population for this study. Socio-demographic and anthropometric
data were collected for each subject. Self-reported and patient
clinical records of established CVD and complications such as
heart failure, stroke, myocardial infarction, angina, peripheral
vascular disease and kidney disease were recorded.
Clinic blood pressure (BP) was measured by trained health
workers in each PHC, according to guidelines of the International
Society of Hypertension (ISH)/World Health Organisation
(WHO) 1999 and the JNC-7.
15,16
Measurements were taken using
a standard mercury Accoson sphygmomanometer (Accoson
works, Vale Road, London N4 1PS) with appropriate cuff size.
Three BP measurements were taken using the subject’s right
arm with the subject in the sitting position after five minutes of
rest, with one minute between measurements. The mean of three
measurements was used as the final value.
Participants with an elevated BP measurement were invited to
attend a second clinic visit after one to two weeks to have their
BP measured again. The average BP of the second visit was
used as a criterion for the diagnosis and control of hypertension.
In addition, all treated hypertensive patients were asked to
return for a second visit after one to two weeks to have their BP
measured.
Hypertension was defined as systolic blood pressure (SBP)
≤
140 mmHg, diastolic blood pressure (DBP)
≤
90 mm Hg, or
current treatment with antihypertensive drugs in subjects with
a history of hypertension.
16,17
Awareness
of hypertension meant
a previous diagnosis of hypertension or high blood pressure.
Controlled hypertension
was defined as treated hypertension
with SBP
<
140 mmHg and DBP
<
90 mmHg at the second
clinic visit.
Each subject underwent further physical examination to
determine clinical features of LVH, CHF, stroke, renal failure, and
fundoscopy for hypertensive retinopathy. Hypertensive cardiac
damage was defined by the presence of electrocardiographic
(ECG) LVH based on the voltage criteria of Araoye
18
in black
hypertensives. LVH was determined as follows: the sum of SV
2
+ RV
6
in males of
≥
40 mm and females of
≥
35 mm and RI
≥
12 mm. These criteria have been shown to correlate better with
echocardiograhic LVH in Nigerians.
19
Hypertensive eye damage
was diagnosed based on the Keith-Wagener classification of
hypertensive retinopathy and the patients were divided into four
grades.
20
Renal damage was diagnosed based on the presence of
microalbuminuria as determined by spot urine albumin-to-
creatinine ratio [ACR (mg/g)]. In males, ACR
<
2.5 mg/g is
normal, 2.5–25 mg/g defines microalbuminuria and
>
25 mg/g
indicates gross proteinuria. In females, ACR
<
3.0 mg/g is
normal, 3.0–30 mg/g defines microalbuminuria, and
>
30 mg/g
indicates gross proteinuria.
21-24
Venous blood samples were obtained via the ante-cubital
vein for biochemical assessment, including fasting serum total
cholesterol, high-density lipoprotein cholesterol (HDL-C) and
fasting blood glucose levels.
Statistical analysis
The data obtained were analysed using SPSS version 13.0
software (SPSS Inc, Chicago, Illinois, USA). Descriptive
analysis of the variables was performed to process the data as
tables. Continuous variables were described by calculating the
means and standard deviation (SD). Categorical variables were
described using frequency tables.
Results
A total of 415 subjects consisting of 184 men (44.3%) and
231 women (55.7%) participated in the study. The baseline
characteristics of the subjects are shown in Table 1. The females
were significantly older [50.4 (
±
13.2) years] than the males
[46.9 (
±
16.7) years] (
p
<
0.001). SBP and DBP did not vary
significantly according to gender. The detection and treatment
rate of hypertension was low in the studied population. Only
14.2% of the subjects had self-reported hypertension and of
these, only 18.6% had been on medications in the past three
months; of whom only 27.3% had controlled blood pressure.
This means that only 5.1% of subjects who had self-reported
hypertension had controlled BP at the time of the study.
The antihypertensive drugs used either alone or in combination
included centrally acting alpha-adrenergic agonists such as
α
-methyl DOPA and Brinerdin (74.3%), thiazide diuretics
(86.1%), calcium channel blockers (15.6%) and ACE inhibitors
(1.7%). Some of the subjects who self-reported hypertension
were on benzodiazepines prescribed as antihypertensives by
their general practitioner.
The prevalence of diabetes among the participants was 9.6%
(7.1% in men and 11.7% in women). The prevalence of smoking
in the study population was 5.1% and all the cigarette smokers
were men.
Table 2 shows the prevalence of hypertensive TOD among
the subjects studied. Overall, 179 (43.1%) of the subjects, 83
(20.0%) men and 96 (23.1%) women, had evidence of TOD.
The age difference between those subjects with (47.4
±
11.5
years) and without (45.9
±
13.2 years) TOD was not statistically
significant (
p
=
0.12). The blood pressure of subjects in relation
